Positive feed system for circular knitting machines

ABSTRACT

An adjustable positive yarn feed system comprises a variable diameter wheel used to drive a band, tape or the like by which positive feed is applied to a yarn or yarns, adjusting means for varying the wheel diameter a stepping motor for effecting incremental variation of the setting of the adjusting means, and a control device for actuating the stepping motor as and when required.

United States Patent Cooke [:51 3,675,446 51 July 11, 1972 [54] POSITIVE FEED SYSTEM FOR CIRCULAR KNITTING MACHINES [72] Inventor: Albert Edward Cooke, Leicester, England [73] Assignee: Trip-Lite Limited, South Wigston, En-

gland [22] Filed: June I6, I970 [2!] Appl. No: 46,736

[30 Fonelgn Application Priority Data June 20, I969 Great Britain ..3l,2I4/69 l5 2| US. Cl .66/132 T, 226/40, 226/41 [5| Int. Cl. A v o I l I t ..D04b 15/48 [58] Field oISearch .r66/l32 T;226/40,4l

[56] References Cited UNITED STATES PATENTS 3,243,09l 3/1966 Rosen ..66/l32TX 3,327,499 6/l967 Schmidt et al .66/l 32 3,478,945 I l/l969 Cooke ..66/l 32 T UX FOREIGN PATENTS OR APPLICATIONS 1,290,290 3/1969 Germany ..66/l 32 T 300,138 4/l968 Sweden 66/132 T Primary ExaminerRobert R. Mackey Attorney-Larson, Taylor and Hines ABSTRACT An adjustable positive yarn feed system comprises a variable diameter wheel used to drive a band, tape or the like by which positive feed is applied to a yarn or yarns. adjusting means for varying the wheel diameter a stepping motor for effecting incremental variation of the setting of the adjusting means, and a control device for actuating the stepping motor as and when required.

ll Chum, 3 Drawing Figures P'A'TENTEDJUL 1 1 1212 SHEET 2 or 3 FIG POSITIVE FEED SYSTEM FOR CIRCULAR KNITTING MACHINES This invention is for improvements in positive feed systems and is concerned more particularly with means for effecting required changes in the rate of positive yarn feed.

In accordance with the invention there is provided a positive yarn feed system, such as may be used on a circular knitting machine, wherein a variable diameter wheel is used to drive a band, tape or the like through the operation of which positive feed is applied to a yarn or yarns and having an adjusting means on the variable diameter wheel, to adjust its diameter, a stepping motor for varying the setting of the adjusting means and a control device for activating the stepping motor as and when required. The stepping motor is conveniently arranged to be activated in such manner as to vary the setting of the adjusting means in small increments forwardly or in reverse to provide for required changes in the ratio of the drive between the variable diameter wheel and the band, tape or the like whereby required changes in the rate of positive feed are effected smoothly and effectively in accordance with pro-determined requirements.

Heretofore it has not been practicable with circular knitting machines for producing stockings, tights, panty-hose or other garments of a shaped nature to provide an effective positive feed arrangement meeting requirements of changes in positive feed rate at different parts of the garments.

It is thought that this arises from the difliculty of providing an accurate and reliable method of varying the rate of supply according to a pre-arranged program and the complexity of control means required. The system in accordance with the invention has been devised with the object in view of largely or wholly meeting all the requirements involved in providing a satisfactory positive feed system in which required alterations in rate of feed can be effected accurately at appropriate times.

in practising the invention the variable diameter wheel conveniently has a cam disc which is arranged to control the radial positions of a series of blocks forming segments of the wheel periphery, and the cam disc is geared to the spindle of the stepping motor to be adjusted by the action of said motor. The variable diameter wheel may be constructed as described in my US. application, Ser. No. 46,340, filed June 15, i970, based on British Application No. 3 l 213/69. With this form of wheel the cam disc positioned at one side and arranged for turning movement to adjust the radial positions of the blocks is conveniently formed peripherally with gear teeth engaged by a pinion at one end of a train of gears driven from the spindle of the stepping motor.

The control device by which the operation of the stepping motor is governed may comprise a photo-electric or other sensing device responsive to indications on a disc which conveniently rotates with the variable diameter wheel and the mounting of the stepping motor, and/or in response to indications on a disc which is driven to rotate at a speed proportional to that of the variable diameter wheel. With such an arrangement the electrical supply to the stepping motor is conveniently provided by a stationary brush unit having brushes engaging with slip rings connected to the motor windings.

A convenient control device is one in which there is a scanning head fitted with two photo-transistors and an opposed lamp or lamps between which a disc as aforesaid is interposed, a single slot or a plurality of slots at circumferential intervals being formed in the disc to provide for exposure of the photo transistors to the light from the lamp or lamps. As each slot passes the scanning head a sequence of four different conditions of energization of the photo transistors occurs namely: exposure of first transistor only; exposure of both transistors, exposure of second transistor only; and non-exposure of both the transistors. Thereby a sequence of different impulses in a particular order is initiated at the scanning head and is used to advance the motor in a succession of four short step movements. The direction of movement of the motor may, if required, be controlled by a switch in an appropriate electrical control circuit through which the impulses are fed to the motor. Thus the stepping movements of the motor impart small adjustments to the variable diameter wheel.

The number of increments of adjustment of the wheel which occur during a rotation of the control disc can be varied in the case of a disc having circumferentially spaced slots by masking one or more of the slots to provide for the required number of energizations of the motor at each rotation of the disc. The incidence of adjusting movements imparted to the variable diameter wheel can be controlled by energization and deenergization of the scanning head and/or circuits controlled thereby, under the dictation of patterning means, e.g. a chain or drum on the knitting machine. Thus during the progress of the knitting operation the scanning head and the circuits controlled thereby will be de-energized during periods when no change in the rate of positive feed of yarn is required and ener gizing of the scanning head and its circuits will occur only during a period when change in the positive feed rate is needed.

The adjustment of the degree of change in rate is determined by the period of energization and the number of slots which are exposed in the control disc. In a case in which it is desired to provide a fine adjustment requiring less than four stepping impulses to be applied to the motor in each rotation of the variable diameter wheel, an auxiliary scanning head related to a disc having a single slot may be provided with such disc driven at a reduced speed from a spindle carrying the variable diameter wheel and the mounting of the stepping motor, for example at a rate of one turn for every four turns of the spindle of the variable diameter wheel. Thus the equipment may have two scanning heads one related to a disc as afore mentioned with a circumferential row of slots and another related to a disc having only one slot which is driven at a slower rate of speed, either scanning head being caused to activate the motor as required.

A convenient form of improved positive feed system is illustrated by way of example in the accompanying drawings in which FIGS. la and lb together show in perspective view with certain parts broken away and mountings omitted, the driving arrangements in the system, and

FIG. 2 is an electrical circuit diagram.

Referring to FIGS. la and 1b there is shown a positive driving belt 10 for driving a gear pulley 11 on a vertical shaft 12 supported in fixed bearings not shown. The belt 10 is driven from a timing pulley on an appropriate shaft of a circular knitting machine which is equipped with positive feed mechanism comprising yarn feeding rollers l3 and i4 driven by a tape or band 15 from a master driving pulley l6 as described in my US. Pat. No. 3,478,945 issued Nov. 18, i969. The pulley 16 is on a spindle l7 driven by a belt 19 which engages with a variable diameter pulley indicated generally at 20 and fixed to the shaft 12. The belt 19 is equipped with a spring urged jockey pulley (not shown) to maintain it in a taut condition.

The variable diameter pulley 20 is constructed as described in my U.S. application, Ser. No. 46,340, filed June 15, 1970, based on British Application No. 31213169 and comprises radially adjustable blocks 21 slidable on pairs of parallel radial spokes 22 radiating from a central holder 23, and a cam disc 24. By turning the disc 24 relatively to the holder 23 the blocks 21 are adjusted radially to vary the effective diameter of the pulley presented by the center parts of the blocks 21 engaged by the belt 19 between the projecting ends of the rods 22. ln practicing the present invention the cam disc 24 is formed with gear teeth 25 around its edge which are engaged by a pinion gear 26, the turning of which causes adjustment of the disc 24 and of the efl'ective diameter of the pulley 20.

It will be understood that while the control holder 23 of the pulley 20 is fixed to the vertical shah 12, the cam disc 24 is mounted so as to be capable of turning on the shaft. Also fixed to the shaft [2 is a carrier disc 27 which supports on four pillars two of which are seen at 28) a stepping motor indicated at 29. The motor 29 has a spindle 30 which carries a gear wheel 31 for driving through a train of gears 32 a gear wheel 33 secured to a spindle to which the pinion 26 is fixed. The gears 32 and 33 have their spindles carried by the carrier disc 27. Also secured to the motor casing concentrically with the shaft 12 is a scanning disc 34 which thus rotates with the shaft 12 and which is formed with spaced slots 35 at a position to pass through a gap in a scanning head 36. The latter is fitted with two photo-transistors side by side and an opposed lamp or lamps, the light from which can be transmitted through one of the slots 35 to energize the photo-transistors. As each slot passes the scanning head a sequence of different impulses is set up and according to the order in which these are applied to the stepping motor it is energized for forward or reverse stepping movements.

The stepping motor 29 receives its energization through slip rings 37 carried on an insulating disc 38 which rotates with the motor 29 and shaft 12. Three of the slip rings supply power to the motor and the fourth is related to a switching circuit. These slip rings are engaged by brushes 39 on a stationary brush unit 40.

Secured to the top of the motor assembly 29in line with the shaft 12 is a further shaft 41 which carries a small pulley 42 driving through a belt 43 a larger pulley 44 supported for rotation by a spindle 45 carried by an arm 46 on a stationary post 47. The pulley 44 has depending from it three symmetrically arranged rods 48 supporting a further scanning disc 49 formed with a single slot 50 to co-operate with a further scanning head 51 fixed to the post 47 and constructed similarly to the scanning head 36.

In the operation of the apparatus illustrated the shaft 12 is driven during the operation of the knitting machine at a speed in synchronization with the machine. Assuming that an article such as a stocking or leg blank for a panty-hose is being knitted it is required that at different times the effective diameter of the variable diameter pulley shall be changed accurately to vary the rate of positive feed of the yarn fed by the rollers 13 and 14, in order to provide the required changes in yarn length or loop size. These changes must be very accurate as well as easy to program and these conditions are well met by the employment of the stepping motor 29 which when supplied with DC. pulses with polarity changes in a specific sequence will turn in the required direction in minute intermittent steps. The motor used at 29 is one which can also be run on AC, this facility being used for re-setting purposes.

When the knitting operation commences with the pulley 20 initially set for the required rate of positive feed the machine proceeds to knit with a loop size determined by the initial rate. 50 long as no change in the rate of positive feed is required the scanning head 36 will have its circuit switched off so that the rotation of disc 34 has no effect on it. When a change in the rate of positive feed is required control means on the machine will cause the scanning head 36 to be switched on for the required direction of movement of the motor spindle to effeet a small increment of change in the diameter of the pulley 20 to increase or decrease it as needed. Thereupon the scanning disc 34 on turning will cause its slots to pass the scanning head 36 to give rise to energization of the motor for small increments of movement as each open slot passes through the scanning head. It will be predetermined how many energizations of the motor 29 are required for each rotation of the disc 34 and the number of eflective slots 35 will be ad justed accordingly by covering a slot or slots in the disc 34 until the required number of effective exposures is left. The period of energization of the scanning head 36 is also controlled to provide for the required number of energizations of the stepping motor 29 to effect the change in pulley diameter.

if a finer degree of change in pulley diameter is required the scanning disc 50 and scanning head 51 are brought into action instead of the disc 34 and head 36, by switching on the scanning head 5!. Four energizations of the motor will be caused during each rotation of the disc 49 and the disc is arranged to rotate at a reduced speed compared with the shaft 12, the ratio being determined by the relative sizes of the pulleys 42 and 44 and being adjustable by substituting a different sized pulley at 42.

Changes in the rate of positive feed are effected as above described by control mechanism of the knitting machine e.g. the patterning chain) at required steps during the knitting of a stocking or leg blank and on completion of the article it is required that the variable diameter pulley 20 shall be restored to its original diameter for commencement of knitting the next article or blank.

To assist such resetting there may be a bracket 52 fixed to the cam disc 24 and having an upturned wing 53 arranged to trip a button 54 of a microswitch 55 supported by a bracket 56 having a clamping screw 57 by which it can be fixed to the carrier disc 27 at any desired position around the periphery thereof. By a switching circuit actuated by the knitting machine control means, stepping motor 29 may be caused to be operated in reverse to step the cam disc 24 round until the wing 53 of bracket 52 trips the micro-switch 55 so as to deenergize the motor 29 when the cam disc 24 has been reset. Advantageously, however, the resetting movement of the cam disc 24 is effected by energizing the motor 29 by A.C. for continuous movement in reverse and using the switch 55 to interrupt such energization. In each case the switch 55 will remain tripped until the wing 53 is moved away from the button 54. This can be brought about by means of a control switch (not shown) which overrides the action of switch 55 for starting purposes.

One particular example of a suitable circuit arrangement for controlling the stepping motor is illustrated in FIG. 2, the motor being shown by its windings at 58 and its slip rings at 37. The photo-transistors of the scanning heads 36 and 51 are indicated at 59 and 60 and they are related to reed switches of change-over type indicated at 61, 62, 63, and 64. Surge suppression circuits 61a, 62a, 63a, and 640 are related respectively to the reed switches, and lamps 65 and 66 are related to the photo-transistors 59 and 60. The circuit is energized from a mains transformer 67 having a center tapped secondary coil 68 connected to a rectifier bridge 69 from which the DC. supply for the impulses is provided as well as a neutral line used in energizing the motor 58. The transformer 67 has an additional secondary coil 70 related to a rectifier bridge 71 from which the 0.0 supply for the lamps 65 and 66, phototransistors 59 and 60 and for operating switch coils is derived. The switch coils just referred to are shown at 72 and 73 and operate multi-contact switches 74 and 75 through which the generated impulses can be applied in required manner to the slip rings 37 through the brushes 39. The circuit is controlled in operation by the switches 76, 77 and 78 which are actuated by cams on the control chain or pattern drum of the knitting machine The switch 78 is ganged with the switch 79 and controls the activation of the stepping motor adjustment sequence by controlling the DC. supply to the photo-transistors 59 and 60. The switch 79 controls the zero volts line to the motor 58. The switch 76 together with switch 77 control activation of the switch coils 72 and 73, respectively. The switch 76 in effect controls which of the scanning heads 59 and 60 is activated. If the switch 76 is open the reed switch pair 61 and 62, pulsed by the phototransistors in the scanning head 59, are connected to the motor 58. 1f the switch 76 is closed, the reed switch pair 63 and 64, pulsed by the photo-transistors in the scanning head 60, are connected to the motor 58. During scanning, the switch 77 must be opened. Thus, in the process of knitting a stocking, the switch 76 is kept open during the knitting of a stocking welt and panel and closed for narrowing while the switch 77 is open for forward energization of the motor coils 58. The switch 77 controls reverse energization of the step motor 58. To this end, the switches 76 and 78 already being open, the switch 77 is closed so as to connect an ac supply to the stepping motor over the switches 75. Reverse energization of the motor 58 is automatically terminated by operation of the switch 55 as previously described.

What I claim is:

1. In a positive yarn feed system for a knitting machine, the combination comprising positively driven yarn feeding rollers, an endless band for driving said rollers, a variable diameter wheel through which said endless band is driven, means for driving the variable diameter wheel, a rotary adjusting means for varying the effective diameter of said variable diameter wheel, a stepping motor, drive connecting means between said stepping motor and said rotary adjusting means, and a control device for activating the stepping motor in predetermined manner.

2. A combination according to claim 1 wherein said control device includes means for activating the stepping motor to vary the setting of the adjusting means in small increments forwardly or in reverse to provide for required changes in the ratio of the drive whereby changes in positive feed rate are effected smoothly and effectively.

3. A combination according to claim 1 wherein the rotary adjusting means includes a cam disc and said drive connecting means comprises gear means connecting said disc to the stepping motor and wherein the variable diameter wheel comprises a series of blocks forming wheel segments which are adjustable radially by the cam disc in response to actuation of the gear means by the stepping motor.

44 A combination according to claim 3 wherein the said cam disc is positioned at one side of the wheel and mounted rotatably for adjustment of the radial positions of said blocks and wherein the gear means include gear teeth peripherally formed on the cam disc and a train of gears driven from the stepping motor including a pinion gear engaging with the gear teeth on the cam disc.

5. A combination according to claim 1 wherein the control device comprises an indicator disc and a sensing device responsive to indications on the disc for controlling operation of the stepping motor.

6. A combination according to claim 5, comprising means mounting the disc to rotate at a speed related to the speed of the variable diameter wheel.

7. A combination according to claim 6 wherein the sensing device comprises a scanning head including two photo transistors and at least one light source and wherein the disc is interposed between the photo transistors and the light source and is formed with at least one indicator slot to provide for exposure of the photo transistors to the light source.

8. A combination according to claim 7 wherein the two phototransistors are mounted peripherally relative to the disc to position them for sequential exposure through a disc slot during rotation of the disc.

9. A combination according to claim 7 in a system for positively feeding yarn to a knitting machine having patterning means, including means for controlling energization and deenergization of the scanning head, said controlling means being constructed and arranged to be actuated under the dictates of the patterning means of the machine.

10. A combination according to claim 7 comprising an auxiliary scanning head and a related auxiliary disc with at least one slot formed therein for scanning by the auxiliary scanning head, and means for driving the auxiliary disc at a speed proportional to but slower than that of the indicator disc.

11. A combination according to claim 10 including means for causing either one of the two scanning heads to actuate the stepping motor in accordance with requirements. 

1. In a positive yarn feed system for a knitting machine, the combination comprising positively driven yarn feeding rollers, an endless band for driving said rollers, a variable diameter wheel through which said endless band is driven, means for driving the variable diameter wheel, a rotary adjusting means for varying the effective diameter of said variable diameter wheel, a stepping motor, drive connecting means between said stepping motor and said rotary adjusting means, and a control device for activating the stepping motor in predetermined manner.
 2. A combination according to claim 1 wherein said control device includes means for activating the stepping motor to vary the setting of the adjusting means in small increments forwardly or in reverse to provide for required changes in the ratio of the drive whereby changes in positive feed rate are effected smoothly and effectively.
 3. A combination according to claim 1 wherein the rotary adjusting means includes a cam disc and said drive connecting means comprises gear means connecting said disc to the stepping motor and wherein the variable diameter wheel comprises a series of blocks forming wheel segments which are adjustable radially by the cam disc in response to actuation of the gear means by the stepping motor.
 4. A combination according to claim 3 wherein the said cam disc is positioned at one side of the wheel and mounted rotatably for adjustment of the radial positions of said blocks and wherein the gear means include gear teeth peripherally formed on the cam disc and a train of gears driven from the stepping motor including a pinion gear engaging with the gear teeth on the cam disc.
 5. A combination according to claim 1 wherein the control device comprises an indicator disc and a sensing device responsive to indications on the disc for controlling operation of the stepping motor.
 6. A cOmbination according to claim 5, comprising means mounting the disc to rotate at a speed related to the speed of the variable diameter wheel.
 7. A combination according to claim 6 wherein the sensing device comprises a scanning head including two photo transistors and at least one light source and wherein the disc is interposed between the photo transistors and the light source and is formed with at least one indicator slot to provide for exposure of the photo transistors to the light source.
 8. A combination according to claim 7 wherein the two phototransistors are mounted peripherally relative to the disc to position them for sequential exposure through a disc slot during rotation of the disc.
 9. A combination according to claim 7 in a system for positively feeding yarn to a knitting machine having patterning means, including means for controlling energization and de-energization of the scanning head, said controlling means being constructed and arranged to be actuated under the dictates of the patterning means of the machine.
 10. A combination according to claim 7 comprising an auxiliary scanning head and a related auxiliary disc with at least one slot formed therein for scanning by the auxiliary scanning head, and means for driving the auxiliary disc at a speed proportional to but slower than that of the indicator disc.
 11. A combination according to claim 10 including means for causing either one of the two scanning heads to actuate the stepping motor in accordance with requirements. 